Many measurement or sensing systems require the processing of analogue signals from a large array of detectors. The processing is generally carried out using a digital sub-system, so analogue-to-digital conversion must be performed on the detector outputs.
The analogue-to-digital converter (ADC) must be able to accommodate many simultaneous inputs, and have large throughput. A conventional approach would be to utilize a small number of fast ADCs, each preceded by an analog multiplexer which selects one of the many analog inputs at a time for conversion. However, this technique has limitations; in particular, the analog multiplexing may introduce noise and errors into the analog signals, and the single ADC may be large (an N-bit flash ADC requires 2.sup.N comparators and the multiplexing hardware will further increase the chip size) and dissipate significant power in order to meet the speed requirements.